When you see the silk bags in your trees near the end of summer, that is the result of the fall webworm. These little pests cause almost no permanent damage to the host tree but they can be very unsightly. Fall webworms are easily seen from August to September. This is when their webs are large and located toward the ends of the branches. People often confuse fall webworms with bagworms but they are two completely different pests.
Most people never see the actual caterpillar that causes the silk webs, but if you run into one, this is what they look like.
- Mature larvae are about an inch long
- Two-color forms
- black heads with yellow/white bodies
- red head with brown bodies
- Paired black tubbers along back
- Covered with long silky hair
- Found in silky webs at the tips of branches
Fall Webworm Habits
These caterpillars feed on over 100 different species of plants but are commonly seen on walnut, hickory, pecan, mulberry, poplar, willow, sweetgum, linden, ash, and most fruit trees. There are 2 generations of this pest per year. Most of the time the first generation in May is smaller and goes unnoticed. The second generation is active late July to August but their remains can be seen into October.
Fall Webworm Control
Fall webworms rarely do permanent damage to trees and therefore treatment is usually not warranted. Pruning out infected branches is a common control method, but in reality, that is doing more damage to the plants than these little insects. BT is a pesticide labeled for control of caterpillars if control is needed for aesthetics. Bt is a bacteria that will kill the target insect but will not harm the beneficial insects.
If you have fall webworms and can’t live with them, give Wellnitz Tree Care a call and we can help you out.